138 PROCEEDINGS OF THE ACADEMY OF {March, 
The average size of 78 living shells is about 19x9 to10 mm. Fig. 
18 represents the largest shell taken, a dead one 26.5 mm. long. There 
is but little variation in sculpture among shells from this place. 
Along the Rio San Filipe, not far from the Rio Grande, in chapparal 
on the east side, we found numerous specimens differing from those 
of Devil’s river by having the rib-strie nearly obsolete on the last 
whorl except just below the suture. A large number of dead shells 
were found, but only very few living ones (pl. VI, figs. 23, 24). They 
have the dull reddish, white-streaked coloration and the shape of the 
Devil’s river ragsdalev. 
Bulimulus dealbatus pecosensis n. subsp. Pl. VI, figs. 26, 27. 
B. d. schiedeanus var., Pilsbry, Man. of Conch., XI, p. 132, pl. 17, fig. 6. 
The shell is conspicuously calcareous, whitish with some fleshy or 
sometimes corneous or ochraceous streaks; upper whorls striate, the 
last somewhat roughened by irregular growth-wrinkles. Spire long, 
composed of numerous short convex whorls, the suture nearly hori- 
zontal; apex white or pale; aperture small, usually ochre-tinted in 
the throat, lip strengthened by a rib within. 
Alt. 31 29.7 26.5 24 22.8 21 mm. 
Diam. 14.8 14 12.8 12 12.7 10.006 
Aperture 15 14 TG 10.3 11.5 HOD e 
Whorls 74 it 74 (ke: 7 7 
Type locality, on the mesa about 14 miles southeast of the eastern 
end of the High Bridge of the Pecos (Southern Pacific Railroad), Val 
Verde county, Texas. We found one small colony of this form, in the 
midst of the large dark-mouthed B. alternatus marie, and like that 
chiefly living on Agave. The extent of the colony was perhaps not 
more than 50 yards, but as the sun had already set, and we had just 
emerged from the labyrinthine side canyons of the Pecos, we had 
time to collect only about thirty-five specimens, each, most of them 
dead. Everywhere else in the region around the High Bridge we 
found only B. a. marie. 
This form is clearly a stunted race of the larger and less slender 
B. schiedeanus of the Mexican fauna. JB. schiedeanus has been con- 
sidered specifically distinct from dealbatus by Binney and all the older 
authorities, as well as by von Martens, who gives a series of good 
figures in the Biologia Centrali Americana; but while the typical 
schiedeanus is distinet enough, there are not lacking specimens sug- 
gesting intergradation with some forms of dealbatus. If schiedeanus 
